The present invention relates to a process for producing olefin polymers or copolymers capable of being controlled in molecular weight as well as novel olefin polymers or copolymers and applications thereof. More particularly, the present invention relates to a process for producing olefin polymers or copolymers of a high molecular weight wherein a polymerization time or an average retention time in a polymerization reactor is adjusted by the aid of a specific metallocene catalyst thereby enabling control of the molecular weight at the time of producing the olefin polymers or copolymers and adjustment of the molecular weight to a higher molecular weight range as well as novel olefin polymers or copolymers and injection moldings excellent in rigidity and heat-resistance, especially molded from polypropylene; films excellent in transparency in addition to the above characteristics; a composition comprising the aforesaid polypropylene and an xcex1-form nucleating agent; a modified composition which is comprised predominantly of the aforesaid polypropylene and a radical generator and has been subjected to melt-kneading treatment; and filaments or fibers or non-woven fabrics of the aforesaid propylene polymers or copolymers.
Olefin polymers or copolymers such as polypropylene or polyethylene are excellent in mechanical properties and chemicals-resistance and are very useful in balance to an economic aspect so that they are employed in the field of various moldings. From the past, these olefin polymers or copolymers were produced by polymerizing or copolymerizing olefins by the aid of a so-called Ziegler-Natta catalyst which is a combination of a transition metal catalytic component comprising titanium trichloride and/or tetrachloride carried on a support such as magnesium chloride with an organoaluminum compound.
In recent years, on the other hand, a process for producing olefin polymers or copolymers by polymerizing or copolymerizing olefins by the aid of a new catalyst different from the conventional catalyst system has widely been utilized, the new catalyst being comprised of a metallocene and an aluminoxane. Olefin polymers or copolymers produced by way of this metallocene catalyst system are distinguished themselves by their narrow molecular weight distribution and by the fact that in case of copolymers, the comonomer has homogeneously been copolymerized therein so that olefin polymers or copolymers which are more homogeneous than the conventional olefin polymers or copolymers can be obtained.
In the production of olefin polymers or copolymers by the aid of such metallocene catalyst system, however, there is a problem that the molecular weight of the resultant olefin polymers or copolymers are generally poor or that the molecular weight of olefin polymers or copolymers obtained at a practical but a higher polymerization temperature are too low to be used practically.
As is seen in Japanese Laid-open Patent Appln. No. Sho. 63-251405, It is known that the molecular weight of olefin polymers or copolymers can be increased by using a metallocene compound including hafnium as a transitions metal. In case of the hafnium compound, however, the polymerization activity is poor and not practical.
In Journal of Molecular Catalysis A: Chemical 102, 59-65 (1995), there is disclosed that the molecular weight of olefin polymers or copolymers can be increased by lowering the polymerization temperature. In case the polymerization temperature is lowered, however, the polymerization activity becomes extremely poor. Thus, such a method cannot be said to be practical, too.
It is disclosed in Japanese Laid-open Patent Appln. No. Hei. 6-100579 that the molecular weight of olefin polymers or copolymers can be increased by using a catalyst wherein the metallocene compound has a complicate structure. In this case, however, the synthetic route of such metallocene compound having a complicate structure becomes complicate so that cost for manufacturing the catalyst becomes too high to be practical. It is also disclosed in Macromol. Symp. 97, 205-216 (1995) that the molecular weight of olefin polymers or copolymers can be increased by increasing the monomer concentration in the polymerization system or raising the polymerization pressure. As is described in the aforesaid Journal of Molecular Catalysis A: Chemical 102, 59-65 (1995), the molecular weight of olefin polymers or copolymers becomes extremely lower by elevating the polymerization temperature up to a practical polymerization temperature. Accordingly, there is a limit for obtaining high molecular weight olefin polymers or copolymers only by increasing the monomer concentration, and it was difficult to obtain high molecular weight olefin polymers or copolymers aimed at especially in the case of using a metallocene compound having a simple structure. Hence, there is a demand for developing a means for increasing the molecular weight without such problem.
In general, crystalline propylene polymers are relatively cheap and possess excellent mechanical properties so that they are employed for manufacturing various moldings such as injection moldings.
According to the intended various concrete applications, however, the resultant polymer is sometimes insufficient in mechanical properties, especially rigidity and heat-resisting property so that there is a limitation in spreading concrete applications of the polymer.
Hence, there is a desire from the past for enhancing rigidity and heat-resisting property of moldings made of crystalline propylene polymers.
With respect to films as moldings, those disclosed in EP 0629631, Japanese Laid-open Patent Appln. No. Hei. 7-149833 and Japanese Laid-open Patent Appln. No. Hei. 8-73532 can be mentioned as examples of applications of isotactic polypropylene obtained by the aid of a metallocene catalyst system. In these examples, copolymerization is carried out to realize high transparency as one of the requisites of films.
Among a wide versatility of applications of polypropylene, a polypropylene composition excellent in rigidity, heat-resisting property and transparency is firstly demanded. For this purpose, a variety of nucleating agents are employed to improve rigidity and heat-resisting property of crystalline propylene polymers.
On the other hand, in Japanese Laid-open Patent Appln. No. Hei. 5-9225 and Japanese Laid-open Patent Appln. No. Hei. 5-32723 a resin of polypropylene type containing a propylene polymer is proposed wherein the position of a main elution peak (Tmax) according to the temperature rising elution chromatography is 117.0xc2x0 C. or at least 118.0xc2x0 C. for the purpose of improving rigidity and heat-resisting property. There is also disclosed that the resin may be incorporated at need with a nucleating agent.
In Japanese Laid-open Patent Appln. No. Hei. 7-10932, it is proposed propylene polymers wherein a percentage by weight of propylene polymers capable of being dissolved in o-dichlorobenzene at 120-135xc2x0 C. is more than the value obtained by the formula:
(40xe2x88x9215 log MFR)xc3x97100xe2x80x83xe2x80x83(I)
wherein MFR stands for a melt flow rate of the propylene polymers, in case of elevating the temperature of o-dichlorobenzene continuously or stepwise to given temperatures to measure the amount of polypropylene eluted at each temperature, for the purpose of improving rigidity and heat-resisting property.
In the applied field of polypropylene, a modified polypropylene composition is demanded which excels in heat-resisting property and in mold processing in the field of fibers on the basis of a narrow molecular weight distribution.
In WO94/28219, there is disclosed that a homopolypropylene of a low melting point obtained by the aid of a metallocene catalyst system is incorporated with a radical generator and the mixture is kneaded to lower the molecular weight of the polypropylene. However, there is neither description nor suggestion in connection with the merit that a specific polypropylene of the present invention having a high melting point can reduce its molecular weight only without affecting its melting point and molecular weight distribution by incorporating therewith a radical generator and then being kneaded as compared with the case of not being incorporated with the radical generator.
From the past, non-woven fabric made of filaments or fibers of propylene polymers finds a wide applications in various fields including medical and hygienic materials such as operation wear, paper diaper, physiological napkin, etc., industrial materials such as packaging materials, oil adsorbents, etc., taking advantage of their suitable physical properties. Especially, the non-woven fabric is preferably used for medical and hygienic materials.
In general, non-woven fabric of propylene polymers are manufactured by spinning the propylene polymers into filaments, laminating the resultant filaments to form a sheet and thermobonding the sheet. For medial and hygienic applications, especially high flexibility and strong tensile strength are required for the non-woven fabric. In case of non-woven fabric formed by partially thermobonding a fibrous sheet with a hot roll such as a heat-embossing roll, tensile strength of the filaments or fibers would be a key factor deciding tenacity of the non-woven fabic since the non-woven fabric is destroyed by cutting of filaments or fibers between thermobonded points if the thermobonding is effected in a good condition.
On the other hand, if non-woven fabric is treated at a higher temperature or heated for a long period of time to attain good thermobonding, the filaments or fibers in sections other than the thermobonded points would be damaged to deteriorate flexibility of the non-woven fabric. In order to obtain non-woven fabric possessing a high tenacity and flexibility, therefore, the filaments or fibers to be used as a material is required to have a high tensile strength and high thermobonding ability. From the past, it is known that a stretch ratio has to be higher to obtain filaments or fibers of a high tensile strength while a stretch ratio has to be lower to obtain filaments or fibers of high thermobonding ability. However, it was extremely difficult to make these opposite characteristics compatible so that filaments or fibers fully satisfying thermobonding ability are preferentially used. Thus, it is the current status that non-woven fabric commonly satisfying high tensile strength and high thermobonding ability has not as yet been obtained.
Accordingly, it is a subject problem of the present invention to provide non-woven fabric possessing a stronger tensile strength and a higher thermobonding ability as well as filaments or fibers for manufacturing the non-woven fabric.
In case copolymerization of monomers is carried out, the melting point of the resultant copolymer is generally depressed so that the resultant film is deteriorated in heat-resisting property and rigidity and is difficult to use in the field where heat-resisting property and rigidity is required. Consequently, polypropylene films are demanded which are excellent in heat-resisting property and rigidity and possess extremely high transparency.
Accordingly, it is an object of the present invention to provide a process for producing high molecular weight olefin polymers or copolymers which enables control of the molecular weight at the time of producing olefin polymers or copolymers by polymerization and adjustment of the molecular weight to a higher molecular weight range by using a specific metallocene catalyst.
It is another object of the present invention to provide novel olefin polymers or copolymers wherein (1) weight average molecular weight (Mw), (2) a ratio of isotactic pentad (mmmm), (3) 2,1- and 1,3-propylene unit content existing in the polymer chain, (4) a ratio of the weight average molecular eight (Mw) to a number average molecular weight (Mn), i.e. (Mw/Mn), and (5) in case of elevating the temperature of o-dichlorobenzene continuously or stepwise up to given temperatures to measure the amount of eluated polypropylene at each temperature, the position of a main elution peak, the amount of components existing in the range of xc2x110xc2x0 C. of the main elution peak, and a ratio of the total amounts of components eluated at a temperature higher than 0xc2x0 C., are defined within specified ranges.
It is further object of the present invention to provide injection moldings excellent in rigidity and heat-resisting property made of polypropylene as a resin material among the aforesaid olefin polymers.
It is still further object of the present invention to provide films excellent in rigidity, heat-resisting property and transparency made of polypropylene as a resin material among the aforesaid olefin polymers.
It is still further object of the present invention to provide a polypropylene composition excellent in rigidity, heat-resisting property and transparency wherein the aforesaid polypropylene has been incorporated with an xcex1-form nucleating agent.
It is still further object of the present invention to provide a polypropylene composition excellent in moldability wherein the aforesaid polypropylene has been incorporated with a radical generator and then the mixture as a main component has been subjected to a melt-kneading treatment to have a narrow molecular weight distribution.
It is still further object of the present invention to provide non-woven fabric excellent in tensile strength and flexibility from filaments or fibers of the aforesaid polypropylene.
The present invention has been proposed to achieve the foregoing objects, and more precisely, an important technical feature of the present invention resides in polymerization of olefins by the aid of a specific metallocene catalyst system and in discovery of suitable applications of the resultant polymers.
According to the present invention, there is provided a process for producing high molecular weight olefin polymers or copolymers at a polymerization temperature within the range of 40-90xc2x0 C. by the aid of a catalyst system comprised predominantly of the following compounds (A), (B) and (C), which comprises polymerizing olefin monomers by the aid of a catalyst system comprised of the compounds (A), (B) and (C) conjointly with an organoaluminum compound (D) whereby the polymerization time or an average retention time in a polymerization reactor is selected within the range of 1-20 hours to make a weight average molecular weight of the resultant olefin polymers or copolymers obtained by gel permeation chromatography adjustable within the range of 30,000-10,000,000 at need:
the compound (A) being a transition metal compound of the general formula:
Q(C5H4xe2x88x92mR1m)(C5H4xe2x88x92mR2n) MXY
wherein (C5H4xe2x88x92mR1m)(C5H4xe2x88x92nR2n) each stand for a substituted cyclopentadienyl group, m and n each stands for an integer of 1-3, R1 and R2 may be the same or different and each stands for a hydrocarbon group with 1-20 carbon atoms, a silicon-containing hydrocarbon group, and a hydrocarbon group forming at least one hydrocarbon ring which may be substituted by hydrocarbon groups connected to two carbon atoms on the cyclopentadienyl ring, with the proviso that a symmetrical plane containing M is not existent in the position on the cyclopentadienyl ring of R1 and R2 and that R1 or R2 is existent in at least one carbon atom adjacent to the carbon atom connected to Q in at least one cyclopentadienyl ring, Q stands for. a bivalent hydrocarbon radical, unsubstituted silylene radical or a hydrocarbon-substituted silylene radical bridging the groups (C6H4xe2x88x92mR1m) and (C6H4xe2x88x92nR2n), M stands for a transition metal Ti, Zr or Hf, and X and Y may be the same or different and each stands for a hydrogen atom, a halogen atom or a hydrocarbon group,
the compound (B) being an aluminoxane, and
the compound (C) being a finely particulate carrier.
According to the present invention, there is also provided a process for producing the aforesaid olefin polymers or copolymers wherein the polymerization time or an average retention time in a polymerization reactor is within the range of 2-12 hours.
According to the present invention, there is further provided a process for producing the aforesaid olefin polymers or copolymers wherein the compound (D) is used in a molar ratio within the range of 1-10,000 moles per mole of the transition metal of the compound (A).
According to the present invention, there is still further provided a process for producing the aforesaid olefin polymers or copolymers wherein the compound (D) is used in a molar ratio within the range of 50-2,000 moles per mole of the transition metal of the compound (A).
According to the present invention, there is still further provided a process for producing the aforesaid olefin polymers or copolymers wherein the compound (D) is selected from triethylaluminum, triisobutylaluminum or a mixture of both in a mixing ratio of 10:90 to 90:10.
According to the present invention, there is still further provided a process for producing the aforesaid olefin polymers or copolymers wherein the compound (A) is dimethylsilylene(2,3,5-trimethylcyclopentadienyl) (2xe2x80x2,4xe2x80x2,5xe2x80x2-trimethylcyclopentadienyl)zirconium dichloride.
According to the present invention, there is still further provided olefin polymers or copolymers wherein:
(1) a weight average molecular weight (Mw) is 30,000-1,000,000,
(2) a ratio of isotactic pentad is 0.900-0.949,
(3) the 2,1- and 1,3-propylene unit in the polymer chain is 0-1 mole %,
(4) a ratio of a weight average molecular weight (Mw) to a number average molecular weight (Mn), i.e. (Mw)/(Mn) is 1.5-3.8, and
(5) in case of elevating the temperature of o-dichlorobenzene continuously or stepwise up to given temperatures to measure the amount of eluated polyolefin at each temperature, the position of a main elution peak is at least 95xc2x0 C. and the amount of components existing in the range of xc2x110xc2x0 C. of the main elution peak is at least 90% of the total amounts of components
eluated at a temperature higher than 0xc2x0 C.
According to the present invention, there is still further provided the aforesaid olefin polymers or copolymers wherein the amount of components existing in the range of xc2x110xc2x0 C. is at least 95% of the total amounts of components dissolved at a temperature higher than 0xc2x0 C.
According to the present invention, there is still further provided the aforesaid olefin polymers or copolymers wherein the melting point of the polymers or copolymers is 147-160xc2x0 C.
According to the present invention, there is still further provided the aforesaid olefin polymers or copolymers wherein an isolation rate of the polymer or copolymer with n-heptane is 0-10%.
According to the present invention, there is still further provided the aforesaid olefin polymers or copolymers wherein the polymer is a homopolymer of propylene, a propylene-olefin random copolymer containing at least 50% by weight of propylene units or a propylene-olefin block copolymer.
According to the present invention, there is still further provided the aforesaid polypropylene produced by the aid of a catalyst system comprised predominantly of the following compounds (A), (B), (C) and (D):
the compound (A) being a transition metal compound of the general formula:
Q(C5H4xe2x88x92mR1m)(C5H4xe2x88x92nR2n)MXY
wherein (C5H4xe2x88x92mR1m) and (C5H4xe2x88x92nR2n) each stand for a substituted cyclopentadienyl group, m and n each stands for an integer of 1-3, R1 and R2 may be the same or different and each stands for a hydrocarbon group with 1-20 carbon atoms, a silicon-containing hydrocarbon group, with the proviso that a symmetrical plane containing M is not existent in the position on the cyclopentadienyl ring of R1 and R2 and that R1 or R2 is existent in at least one carbon atom adjacent to the carbon atom connected to Q in at least one cyclopentadienyl ring, Q stands for a bivalent hydrocarbon radical, unsubstituted silylene radical or a hydrocarbon-substituted silylene radical bridging the groups (C5H4xe2x88x92mR1m) and (C5H4xe2x88x92nR2n) M stands for a transition metal Ti, Zr or Hf, and k and Y may be the same or different and each stands for a hydrogen
atom, a halogen atom or a hydrocarbon group,
the compound (B) being an aluminoxane,
the compound (C) being a finely particulate carrier, and
the compound (D) an organoaluminum compound.
According to the present invention, there is still further provided the aforesaid polypropylene wherein the compound (A) is dimethylsilylene(2,3,5-trimethylcyclopentadienyl) (2xe2x80x2,4xe2x80x2,5xe2x80x2-trimethylcyclopentadienyl)zirconium dichloride.
According to the present invention, there is still further provided moldings manufactured from the aforesaid polypropylene.
According to the present invention, there is still further provided the aforesaid polypropylene wherein
(1) a ratio of isotactic pentad (mmmm) is 0.900-0.949,
(2) the 2,1- and 1,3-propylene units in the polymer chain is 0-1 mole %,
(3) a weight average molecular weight (Mw) is 40,000-1,000,000,
(4) a ratio of a weight average molecular weight (Mw) to a number average molecular weight (Mn), i.e. (Mw)/(Mn) is 1.5-3.8, and
(5) in case of elevating the temperature of o-dichlorobenzene continuously or stepwise up to given temperatures to measure the amount of eluated polypropylene at each temperature, the position of a main elution peak is at least 95xc2x0 C. and the amount of components existing in the range of xc2x110xc2x0 C. of the main elution peak at least 90% of the total amounts of components eluated at a temperature higher than 0xc2x0 C.
According to the present invention, there is still further provided the aforesaid polypropylene wherein the melting point is 147-160xc2x0 C.
According to the present invention, there is still further provided the aforesaid polypropylene wherein an isolation rate of the polymer with n-heptane is 0-10%.
According to the present invention, there is still further provided injection moldings of polypropylene manufactured from the aforesaid polypropylene.
According to the present invention, there is still further provided polypropylene films manufactured from the aforesaid polypropylene.
According to the present invention, there is still further provided a polypropylene composition wherein the aforesaid polyprolylene in an amount of 100 parts by weight is incorporated with 0.0001-1 part by weight of an xcex1-form nucleating agent.
According to the present invention, there is still further provided the aforesaid polypropylene composition wherein the xcex1-form nucleating agent is at least one selected from the group consisting of talc, a metal salt of an aromatic carboxylic acid, a dibenzylidenesorbitol compound, a metal salt of an aromatic phosphoric acid, poly(3-methyl-1-butene), polyvinylcyclohexane and polyallyltrimethylsilane.
According to the present invention, there is still further provided a modified polypropylene composition wherein the aforesaid polypropylene in an amount of 100 parts by weight has been incorporated with a radical generator in an amount of 0.001-0.5 parts by weight and then the mixture as a main component has been subjected to a melt-kneading treatment.
According to the present invention, there is still further provided polypropylene filaments or fibers having an elongation of at least 200% molded from the aforesaid polypropylene.
According to the present invention, there is still further provided non-woven fabric made of the aforesaid polypropylene filaments or fibers.